Atomization of molten metals is mainly accomplished by two methods: (1) jet atomization, wherein a stream of gas or liquid under high pressure impinges against a stream of the melt or (2) wheel or centrifugal atomization, in which the melt stream flows onto a rapidly rotating disc. Powders produced by either of these methods have a broad distribution of particle sizes. For most uses, it is the smaller sizes which have the greatest utility, necessitating sieving or other means of classification. The oversize is usually recycled, adding to the cost of the final product through melt and heat losses.
FIG. 1 of U.S. Pat. No. 2,630,623 depicts a conventional gas-atomizing process in which a jet of inert gas is impinged on a stream of molten metal in order to break it into droplets. FIG. 1 of U.S. Pat. No. 3,021,562 shows apparatus in which an electrical potential is maintained between a supply of solid metal and an electrode. A process and apparatus for the production of metal powder by atomization of a wire fed against a rotating, water-cooled, vibrating electrode are described by G. Matei, E. Bicsak, W. J. Huppmann and N. Claussen in "Atomization of Metal Powders Using the Vibrating Electrode Method", Modern Der. in P/M, Vol. 9, P/M Prin. and Prod. Proc., Hausner et al Eds., M/P Ind. Fed., A.M.P.I., Box 2054, Princeton, N.J. 08540.